All of lore.kernel.org
 help / color / mirror / Atom feed
From: Frederic Weisbecker <frederic@kernel.org>
To: Juri Lelli <juri.lelli@redhat.com>
Cc: fweisbec@gmail.com, tglx@linutronix.de, mingo@kernel.org,
	linux-rt-users@vger.kernel.org, peterz@infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] tick/sched: update full_nohz status after SCHED dep is cleared
Date: Wed, 20 May 2020 19:02:16 +0200	[thread overview]
Message-ID: <20200520170215.GB8800@lenoir> (raw)
In-Reply-To: <20200520164925.GM10078@localhost.localdomain>

On Wed, May 20, 2020 at 06:49:25PM +0200, Juri Lelli wrote:
> On 20/05/20 18:24, Frederic Weisbecker wrote:
> 
> Hummm, so I enabled 'timer:*', anything else you think I should be
> looking at?

Are you sure you also enabled timer_expire_entry?
Because:

> 
> ...
> ksoftirqd/13-117   [013]   148.265945: softirq_entry:        vec=1 [action=TIMER]

...the timer softirq keep triggering without any timer callback executed. If that's the
case, we may be dealing with an interesting issue.

Thanks.

> ksoftirqd/13-117   [013]   148.265947: softirq_exit:         vec=1 [action=TIMER]
> ksoftirqd/13-117   [013]   148.265948: softirq_entry:        vec=7 [action=SCHED]
> ksoftirqd/13-117   [013]   148.265950: softirq_exit:         vec=7 [action=SCHED]
> ksoftirqd/13-117   [013]   148.265952: sched_switch:         ksoftirqd/13:117 [120] S ==> sysjitter:2536 [120]
>    sysjitter-2536  [013]   148.266912: local_timer_entry:    vector=236
>    sysjitter-2536  [013]   148.266914: hrtimer_cancel:       hrtimer=0xffff9807df91bee0
>    sysjitter-2536  [013]   148.266916: hrtimer_expire_entry: hrtimer=0xffff9807df91bee0 now=148249107837 function=tick_sched_timer/0x0
>    sysjitter-2536  [013]   148.266918: softirq_raise:        vec=1 [action=TIMER]
>    sysjitter-2536  [013]   148.266920: softirq_raise:        vec=7 [action=SCHED]
>    sysjitter-2536  [013]   148.266922: hrtimer_expire_exit:  hrtimer=0xffff9807df91bee0
>    sysjitter-2536  [013]   148.266924: hrtimer_start:        hrtimer=0xffff9807df91bee0 function=tick_sched_timer/0x0 expires=148250105422 softexpires=148250105422
>    sysjitter-2536  [013]   148.266926: local_timer_exit:     vector=236
>    sysjitter-2536  [013]   148.266930: sched_wakeup:         ksoftirqd/13:117 [120] success=1 CPU:013
>    sysjitter-2536  [013]   148.266932: tick_stop:            success=0 dependency=SCHED
>    sysjitter-2536  [013]   148.266934: irq_work_entry:       vector=246
>    sysjitter-2536  [013]   148.266936: irq_work_exit:        vector=246
>    sysjitter-2536  [013]   148.266937: tick_stop:            success=0 dependency=SCHED
>    sysjitter-2536  [013]   148.266940: sched_switch:         sysjitter:2536 [120] R ==> ksoftirqd/13:117 [120]
> ksoftirqd/13-117   [013]   148.266943: softirq_entry:        vec=1 [action=TIMER]
> ksoftirqd/13-117   [013]   148.266946: softirq_exit:         vec=1 [action=TIMER]
> ksoftirqd/13-117   [013]   148.266946: softirq_entry:        vec=7 [action=SCHED]
> ksoftirqd/13-117   [013]   148.266948: softirq_exit:         vec=7 [action=SCHED]
> ksoftirqd/13-117   [013]   148.266950: sched_switch:         ksoftirqd/13:117 [120] S ==> sysjitter:2536 [120]
>    sysjitter-2536  [013]   148.267912: local_timer_entry:    vector=236
>    sysjitter-2536  [013]   148.267914: hrtimer_cancel:       hrtimer=0xffff9807df91bee0
>    sysjitter-2536  [013]   148.267916: hrtimer_expire_entry: hrtimer=0xffff9807df91bee0 now=148250107750 function=tick_sched_timer/0x0
>    sysjitter-2536  [013]   148.267918: softirq_raise:        vec=1 [action=TIMER]
>    sysjitter-2536  [013]   148.267920: softirq_raise:        vec=7 [action=SCHED]
>    sysjitter-2536  [013]   148.267922: hrtimer_expire_exit:  hrtimer=0xffff9807df91bee0
>    sysjitter-2536  [013]   148.267924: hrtimer_start:        hrtimer=0xffff9807df91bee0 function=tick_sched_timer/0x0 expires=148251105422 softexpires=148251105422
>    sysjitter-2536  [013]   148.267926: local_timer_exit:     vector=236
>    sysjitter-2536  [013]   148.267929: sched_wakeup:         ksoftirqd/13:117 [120] success=1 CPU:013
>    sysjitter-2536  [013]   148.267931: tick_stop:            success=0 dependency=SCHED
>    sysjitter-2536  [013]   148.267934: irq_work_entry:       vector=246
>    sysjitter-2536  [013]   148.267936: irq_work_exit:        vector=246
>    sysjitter-2536  [013]   148.267937: tick_stop:            success=0 dependency=SCHED
>    sysjitter-2536  [013]   148.267940: sched_switch:         sysjitter:2536 [120] R ==> ksoftirqd/13:117 [120]
> ksoftirqd/13-117   [013]   148.267943: softirq_entry:        vec=1 [action=TIMER]
> ksoftirqd/13-117   [013]   148.267945: softirq_exit:         vec=1 [action=TIMER]
> ksoftirqd/13-117   [013]   148.267946: softirq_entry:        vec=7 [action=SCHED]
> ksoftirqd/13-117   [013]   148.267947: softirq_exit:         vec=7 [action=SCHED]
> ksoftirqd/13-117   [013]   148.267949: sched_switch:         ksoftirqd/13:117 [120] S ==> sysjitter:2536 [120]
>    sysjitter-2536  [013]   148.268865: call_function_single_entry: vector=251
>    sysjitter-2536  [013]   148.268867: call_function_single_exit: vector=251
>    sysjitter-2536  [013]   148.268870: tick_stop:            success=1 dependency=NONE
>    sysjitter-2536  [013]   148.268872: hrtimer_cancel:       hrtimer=0xffff9807df91bee0
>    sysjitter-2536  [013]   148.268876: call_function_single_entry: vector=251
>    sysjitter-2536  [013]   148.268878: call_function_single_exit: vector=251
> ...
> 
> it looks like tick sched timer is kept armed until tick_stop
> succedes (because of the check performed after _single_exit)?
> 
> Thanks for your quick reply!
> 

  reply	other threads:[~2020-05-20 17:02 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-20 14:04 [RFC PATCH] tick/sched: update full_nohz status after SCHED dep is cleared Juri Lelli
2020-05-20 16:24 ` Frederic Weisbecker
2020-05-20 16:49   ` Juri Lelli
2020-05-20 17:02     ` Frederic Weisbecker [this message]
2020-05-20 18:47       ` Juri Lelli
2020-05-21  0:44         ` Frederic Weisbecker
2020-05-21 17:00           ` Juri Lelli
2020-06-15 15:05             ` Juri Lelli
2020-06-15 21:07             ` Frederic Weisbecker
2020-06-16  6:57               ` Juri Lelli
2020-06-16 20:46                 ` Frederic Weisbecker
2020-06-29 12:36                   ` Juri Lelli
2020-06-29 12:42                     ` Frederic Weisbecker
2020-06-29 12:53                       ` Juri Lelli

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200520170215.GB8800@lenoir \
    --to=frederic@kernel.org \
    --cc=fweisbec@gmail.com \
    --cc=juri.lelli@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-rt-users@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.